I am looking to run 23.5x10x15 track rubber on the old Z, essentially 255/15s.

I have a ton of wheel options but don't have samples to test fit so I am wondering if these will fit under the fenders with a minimum amount of "rolling" the arches.

There are lots of 15x10s available at a 4.5 inch backspace.

Searching here says that a 10 inch 4.5 backspace is ideal.

Here's what I'm looking at:

Wheels and Parts, Wheels from Speedway Motors, America's Oldest Speed Shop

Anyone have good info on what to do here?

That's a very wide rim. I doubt if it'll fit but I've never tried it. We run 15x7 with 0 offset (Konig Rewinds and Panasports) with a 225/50 Hankook or Hoosier tire. We use coil overs and roll the fenders. No flaring is allowed.

Are you planning to do track days or something?

Chuck

I do track the car with NASA and a local vintage group. So zero offset on a 7 incher means 3.5 inch of backspace correct? If that is correct I would be putting the face of the rim .5 closer to the fender/quarter than your set up. (3 inches wider, 1.5 inch more each side, backspace increased 1 inch.) So sound to me like from your experience I would have to switch to coilovers, run a 5 inch backspace, and roll the fenders. I can't switch to coilovers for the vintage thing so I guess this idea is out.

All of this headache is to try to be competitive under one sanctioning body and legal under the other.

Keep in mind that the 7" dimension is the interior. Exterior dimension of that wheel will be more like 8"' which means a 4" backspacing with zero offset. Add to this another 1/2" or so for tire bulge beyond beyond the rim and you'll get a better idea of the total clearance that you need.

I know how my 15x7 wheels w/225 tires fill up the fenders so I just can't see a 10" wide wheel and 255 tire fitting without a major rub. You might want to consider getting a set of the Rewinds ($400 or so) and using someone's old race tires ($100/set?). I wish I could help more but we're limited to a 15x7 wheel.

I remember reading about others using an 8" rim and maybe a 245 tire.

Chuck

Thanks Chuck. I think you guys gave me what I need. There is just no real way to do this. They just aren't going to fit up in the fenders without doing something that would break another rule some place...In the vintage series I am also limited to 7 inch and since this car was raced in the 70's I don't want to lose the ability to go vintage racing. On the right tire I could handle the modern cars with the old Z in NASA PTE, but not in vintage racer trim.